An MR scan for suspected prostate cancer can boost diagnostic accuracy and cut down on as many as 27 percent of biopsies – for those men with nonaggressive cancers.

It could also reduce the number of those overdiagnosed, according to the study.

"Prostate cancer has aggressive and harmless forms. Our current biopsy test can be inaccurate because the tissue samples are taken at random,” noted lead author Dr. Hashim Ahmed, from University College London Hospitals, whose study was reported in The Lancet.
“This means it cannot confirm whether a cancer is aggressive or not and can miss aggressive cancers that are actually there,” he observed, adding that this can lead to misdiagnosis and overtreatment, as well as side effects from unneeded biopsies.

The study suggested that as many as 5 percent of men whose cancers will never give them any health trouble are overdiagnosed, said Ahmed.

The diagnostic dilemma is due to the fact that prostate symptoms or an elevated PSA protein blood level will lead to a biopsy at present. That translates to 100,000 of these procedures in the U.K. alone each year. But PSA tests are not always accurate – which leads to unneeded biopsies.

To see if multi-parametric MR (MP-MR) scanning could cut down on these, the researchers looked at 576 men who had indications of prostate cancer, and gave them scans. The patients were then biopsied – once with template mapping (TPM) and then with a transrectal ultrasound-guided biopsy (TRUS).

TPM biopsies determined that 40 percent of the patients had aggressive cancers. MP-MR scans agreed with these findings 93 percent of the time – but the commonly used TRUS biopsy was accurate only 48 percent of the time.

Moreover, 89 percent of those with a negative MP-MR scan turned out to have no, or harmless, cancer.

"Our results show that MP-MR should be used before biopsy,” stated Ahmed. But, he advised, "while combining the two tests gives better results than biopsy alone, this is still not 100 percent accurate, so it would be important that men would still be monitored after their MP-MR scan. Biopsies will still be needed if an MP-MR scan shows suspected cancer too, but the scan could help to guide the biopsy so that fewer and better biopsies are taken."

Also important, 44 patients had “serious adverse reactions” during the study – all of which were the results of biopsies rather than the scans.

In June, 2016, there was more word of use of MR to detect prostate cancer when a Canadian trial came underway.

“The question is: if someone has a negative MR — do they still need a biopsy?” Dr. Laurence Klotz, lead researcher from the Sunnybrook Research Institute in Toronto, told HCB News. “If you can show that the MR is good enough to be able to say they are very unlikely to have significant cancer, then that would be a huge step forward.”

But using MR isn’t a black or white issue. If someone has a high PSA and other risk factors, then regardless of the scan, a biopsy is probably called for.

A widespread use of MR to diagnose prostate cancer would also be complicated by need for many more experts at interpreting the findings.

And scans can pose cost challenges as well. In Ontario, for example, you can't get an MR covered without a prior biopsy.

“We could have the best data in the world, but if the insurance folks drag their heels before they will agree to fund it, that also will slow things,” said Klotz.

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